Post-construction anchor, and drill bit for drilling prepared holes therefor

ABSTRACT

An anchor  1  adapted to an undercut-type prepared hole  19  having near the hole bottom thereof a diameter expanded in a taper way and including a sleeve  2  having an expansion part  6  and a plug  3  formed with a tapered part  14  inserted into the sleeve  2  for expanding the expansion part  6 . When the plug  3  is hammered with the sleeve  2  contacting the bottom of the prepared hole, an annular projecting part  13  and an engagement groove  7  are engaged in a concavo-convex way as the expansion part  6  expands to contact a tapered surface  21   a  of the prepared hole  19 . At the same time, by a hole-bottom reaction force generated by the plug  3  contacting the bottom of the prepared hole  19 , a construction is completed with the expansion part  6  making press contact with the tapered surface  21   a  of the prepared hole. Concurrently with completion of the construction, the tensile strength equal to that of the steel product and the like can be obtained immediately without adding an external tensile force.

TECHNICAL FIELD

The present invention relates to improvements in a post-constructionanchor that is buried in an existing concrete structure and the likeafter the concrete structure is drilled, and more particularly, to amechanical and undercut-type post-construction anchor that can obtainthe pulling resistance equal to the tensile strength of steel productsand the like.

BACKGROUND ART

Conventionally, there are various structures as this type ofpost-construction anchor. Particularly, in recent years, because of ademand of earthquake-resistant reinforcement and the like, a so-calledundercut-type post-construction anchor is proposed that can obtain thepulling resistance equal to the tensile strength of steel products andthe like (refer, for example, to a brochure of WO 01/06070).

More specifically, the typical post-construction anchor comprises asleeve having an expansion part and a plug (expanding member) insertedthereinto for expanding the expansion part. Basically, after insertingthe anchor into a prepared hole, the plug or sleeve itself is hammeredto expand the expansion part by relative displacement between the two,and then the sleeve is fixed as anchor to the concrete structure and thelike. On the other hand, the undercut-type post-construction anchor isdesigned to obtain an anchor effect such that a prepared hole is drilledbeforehand in a concrete structure where the anchor is to be buried, thehole bottom thereof is extended in a taper (skirt) way or in a truncatedcone in a cross-section, and the expansion part of a sleeve is expandedand then closely contacted with the tapered surface. It is considered todramatically enhance pulling resistance as compared with the case wherea typical straight hole is uses as prepared hole.

However, with the undercut-type post-construction anchors having beenproposed so far, the anchor in itself cannot self-maintain the state ofclosely contacting the expansion part with the tapered surface of theprepared hole, still leaving room for improvement.

More specifically, once the expansion part is expanded in order toclosely contact with the tapered surface of the prepared hole, it isaccompanied by springback more or less. Thus, the close contact state isinsufficient, and the expansion part does not conform and closelycontact with the tapered surface until the pulling force is loaded. Onthe other hand, when the pulling force is unloaded, the close contactstate of the expansion part with the tapered surface of the preparedhole again becomes insufficient, and a clearance might be createdtherebetween. Therefore, when the pulling force is again loaded afterunloaded, the initial load might unfavorably produce the pullout of theanchor.

The invention has been made as focusing attention on these problems.Particularly, an object is to provide an undercut-type post-constructionanchor which can immediately obtain the pulling resistance equal to thetensile strength of the steel product and the like without relying onthe external pulling force and the like once the construction iscompleted, and can self-maintain that state for a long time.

Furthermore, an object is to provide an undercut-type post-constructionanchor in consideration that the state of construction being completedcan be obtained as a tactile feel once the construction is completed,skills are not required in construction, and variations of individualbuilders are not produced in the constructed state.

DISCLOSURE OF THE INVENTION

An invention as claimed in claim 1 is directed to a post-constructionanchor comprising a sleeve having an expansion part and a plug formedwith a tapered part inserted into the sleeve for expanding the expansionpart, the anchor being adapted to an undercut-type prepared hole havingnear a bottom thereof a diameter expanded in a taper way, characterizedin that when the plug is hammered with the sleeve contacting the bottomof the prepared hole, an inner peripheral surface of the expansion partis engaged with an outer peripheral surface of the plug in aconcavo-convex way as the expansion part expands until the expansionpart makes close contact with the tapered surface of the prepared holein accordance with relative displacement between the expansion part andthe plug, and that, at the same time, by a hole-bottom reaction forcegenerated by the plug contacting the bottom of the prepared hole,construction is completed with the expansion part making press contactwith the tapered surface of the prepared hole.

Here, as claimed in claim 2, in terms of obtaining a tactile feelconcurrently with completion of the construction, it is more desirablethat an annular engagement groove is formed in the inner peripheralsurface of the expansion part, and an annular projecting part is formedon the outer peripheral surface of the plug, and that the engagementgroove is engaged with the annular projecting part in a concavo-convexway when the expansion part expands to contact the tapered surface ofthe prepared hole in accordance with the relative displacement betweenthe expansion part and the plug.

Furthermore, as claimed in claim 3, it is desirable that, with theexpansion part being unexpanded, a flange part at a distal end of theplug is locked at an inner periphery opening edge at a distal end of thesleeve for preventing disengagement of the sleeve from the plug.Moreover, as claimed in claim 4, it is more desirable that, with theexpansion part being unexpanded, the outer peripheral surface of theplug is engaged with the inner peripheral surface of the sleeve in aconcavo-convex way for preventing disengagement of the plug from thesleeve, and as a consequence, the flange part at the distal end of theplug is locked at an inner periphery opening edge at the distal end ofthe sleeve for preventing disengagement of the sleeve from the plug.

Therefore, in the invention as claimed in claims 1 to 4, by hammering ofthe plug, the tapered surface of the plug expands gradually outwardlythe expansion part of the sleeve in a skirt way. Concurrently with theexpansion part making close contact with the tapered surface of theprepared hole, the inner peripheral surface of the expansion part isengaged with the outer peripheral surface of the plug in aconcavo-convex way, and then the construction is completed when the plugcontacts the bottom of the prepared hole.

At this time, a tactile feel can be obtained by the concavo-convexengagement of the inner peripheral surface of the expansion part withthe outer peripheral surface of the plug, that is, the concavo-convexengagement of the engagement groove of the inner peripheral surface ofthe expansion part with the annular projecting part of the outerperipheral surface of the plug. In addition, impact sound changessuddenly when the plug contacts the bottom of the prepared hole, therebyallowing easy realization of completion of the construction.

Then, in the state of completion of the construction, the expansion partmakes close contact with the tapered surface of the prepared hole by areaction force from the tapered surface of the prepared hole. Inaddition to the concavo-convex engagement, a hole-bottom reaction forcegenerated by the plug contacting the bottom of the prepared hole pushesback the plug itself in the direction opposite to the hammeringdirection. Consequently, the hole-bottom reaction force works as a forceof further expanding the expansion part in the concavo-convex engagementpart. This is nothing more or less than bringing the expansion part intopress contact with the tapered surface of the prepared hole all thetime. The state of completion of the construction is self-maintained,failing to cause insufficient press contact or occurrence of aclearance. With this, concurrently with completion of the construction,the pulling resistance equal to the tensile strength of the steelproduct and the like can be obtained immediately by the anchor alonewithout relying on an external pulling force and the like.

More specifically, according to the invention as claimed in claims 1 and2, concurrently with completion of the construction, the pullingresistance equal to the tensile strength of the steel product and thelike can be obtained immediately without relying on an external pullingforce and the like. Therefore, this provides not only a greatcontribution to an improvement in performance of the anchor withoutinsufficient anchor effect, nor possible disengagement of the anchor,but also possibility of self-maintaining the state with excellentpulling resistance for a long time.

In addition, once the construction is completed, the state of completionof the construction can be realized at least by occurrence of a tactilefeel and change in impact sound. Thus, no skills are required forconstruction, and no variations due to builders are generated in theconstruction state, achieving excellent workability as well.

Moreover, according to the invention as claimed in claims 3 and 4,anti-disengagement is substantially provided to the plug and the sleeve,thus achieving not only excellent handling-ability, but also excellentworkability, particularly, without having disengagement of one membereven upon upward construction.

The invention as claimed in claim 5 is made on the premise of recitationof any one of claims 1 to 4 to further specify the shape of the preparedhole, and is characterized in that the prepared hole is formed with astraight hole part having a diameter smaller than that of a preparedhole general part, the straight hole part being continuously formed witha bottom of a tapered hole part having a diameter expanded in a taperway, and that the unexpanded expansion part contacts the bottom of thetapered hole part prior to expansion of the expansion part, whereas thedistal end of the plug contacts a bottom of the straight hole part uponcompletion of the construction.

Thus, according to the invention as claimed in claim 5, when the anchoris inserted into the prepared hole, the unexpanded expansion partcontacts the bottom of the tapered hole part to restrict its position,so that the position of the tapered hole part and that of the expansionpart coincide with each other only after this time point.

More specifically, according to the invention as claimed in claim 5, bythe expansion part contacting the bottom of the tapered hole part, thepositions of the two can accurately coincide with each other due to theprepared hole of particular shape, having an advantage of possibleprevention of occurrence of incomplete construction.

The invention as claimed in claim 6 is made on the premise of claim 5,and is characterized in that the plug is formed in a stepped shank, andthat the unexpanded sleeve is inserted into and supported in asmall-diameter shank part to thereby set an outer diameter of a generalpart of the plug and that of a general part of the unexpanded sleeve atroughly the same dimension.

Therefore, according to the invention as claimed in claim 6, insertionof the anchor into the prepared hole can be carried out smoothly.

More specifically, according to the invention as claimed in claim 6, theouter diameter of the sleeve and that of the general part of the plugare formed substantially at roughly the same dimension, thus having anadvantage that smooth insertion of the anchor into the prepared hole canbe carried out more smoothly.

The invention as claimed in claim 7 is made on the premise of any one ofclaims 1 to 6 to clearly define that the plug is formed with a femalethread part considering coupling of a counterpart member to the anchor.It is without saying that a male thread part can be formed in the pluginstead of the female thread part as required.

Likewise, the invention as claimed in claim 8 is made on the premise ofany one of claims 1 to 6 to clearly define that the plug is a deformedbar for reinforced concrete. This deformed bar is used, for example, asa joint bar for earthquake-resistant reinforcement of a concretestructure.

Thus, according to the invention as claimed in claims 7 and 8, the sameadvantages as those of the invention as claimed in claims 1 and 2 can beobtained.

Furthermore, the invention as claimed in claim 9 clearly defines thathelical grooves of thread groove shape are formed in the outerperipheral surface of the plug, considering the concurrent use of anadhesive.

Therefore, according to the invention as claimed in claim 9, the helicalgrooves are formed in the outer peripheral surface of the plug, thushaving an advantage that the adhesive is surely held when usedconcurrently, for example, in addition to an anchor effect of the anchoritself.

The invention as claimed in claim 10 is made on the premise of theinvention as claimed in any one of claims 1 to 9, and is characterizedin that the plug is formed with a restraint ring which can receive apart of the sleeve, and that, at the final stage of expanding theexpansion part, an end of the restraint ring abuts on the outerperipheral surface of the expansion part to restrain an expanded bendpart.

In this case, as claimed in claim 11, in terms of improving the accuracyof relative positioning between the two, it is desirable that a grooveengaged with the end of the restraint ring is formed in the outerperipheral surface of the expansion part. Moreover, as claimed in claim12, it is desirable that the restraint ring is fixed to the plugbeforehand by press-fit or welding.

Thus, according to the invention as claimed in claims 10 to 12, theexpansion part, which is a part of the sleeve, expands outwardly bybeing pressed from the inside by the plug in accordance with therelative displacement between the sleeve and the plug, and at the sametime, parts of the sleeve other than the expansion part gradually comeinto the restraint ring. On the other hand, when expansion of theexpansion part comes at the final stage, the end of the restraint ringabuts on the outer peripheral surface of the expanded expansion part. Inthe case where the groove is formed in the outer peripheral surface ofthe expansion part, the end of the restraint ring is engaged with thegroove. Thus, expansion of the expansion part, and by extension, theconstruction, is completed with the expanded bend part of the expansionpart restrained by the plug from the inside and by the restraint ringfrom the outside.

This is nothing more or less than autonomously locking the expansionstate of the expansion part by the anchor itself, and not by theprepared hole, stabilizing the expansion state of the expansion part andproviding a significant advantage in terms of preventing springback ofthe expansion part.

Here, as claimed in claim 2 or 3, even with the engagement groove of theinner peripheral surface of the expansion part and the annularprojecting part of the outer peripheral surface of the plug are engagedin a concavo-convex way, when an external force in the disengagementdirection works on the plug, for example, to cause slight relativedisplacement of the plug and the sleeve in the axial direction, theexpanded expansion part making press contact with the tapered surface isgoing to return to the diameter decreasing direction. Thus, a clearancecan be produced between the expansion part and the counterpart taperedsurface.

Then, as countermeasures against this problem, as claimed in claim 13,it is desirable that the annular projecting part of the outer peripheralsurface of the plug at a part near the top includes a cylindricalstraight part, and that when the expansion part expands to contact thetapered surface of the prepared hole, a part of the engagement groovemakes close contact with a part of the straight part. At the same time,as claimed in claim 14, it is desirable that the prepared hole is formedwith a straight hole part having a diameter smaller than that of aprepared hole general part, the straight hole part being continuouslyformed with a bottom of the tapered hole part having a diameter expandedin a taper way, and that the unexpanded expansion part contacts thebottom of the tapered hole part prior to expansion of the expansionpart, whereas the distal end of the plug contacts a bottom of thestraight hole part upon completion of the construction.

Consequently, even when an external force in the disengagement directionworks on the plug, for example, to cause slight relative displacement ofthe plug and the sleeve in the axial direction, sufficientcountermeasures can be taken against the at least expanded expansionpart which makes press contact with the tapered surface being going toreturn to the diameter decreasing direction, as long as the straightpart of the annular projecting part makes close contact with a part ofthe engagement groove. This provides a further enhancement in pullingresistance.

The invention as claimed in claim 15 is made on the premise of claim 14,and is characterized in that the expansion part has an expanding clawand an auxiliary expanding claw on the root side of the expanding claw,and that, in parallel with the expanding claw part making press contactwith the tapered surface of the tapered hole part, the auxiliaryexpanding claw is plastically deformed and engaged in an innerperipheral surface of the prepared hole general part upon completion ofthe construction.

Therefore, according to the invention as claimed in claim 15, inaddition to an anchor effect due to press contact of the expanding clawwith the tapered surface of the tapered hole part, another anchor effectis exerted by engaging the auxiliary expanding claw with the innerperipheral surface of the prepared hole general part. This leads to afurther enhancement in pulling resistance.

In this case, it is more advantageous, in terms of preventing theexpanded expansion part making press contact with the tapered surfacefrom returning to the diameter decreasing direction, if it is set, asclaimed in claim 16, such that the construction is completed with adistal end surface of the expansion part makes press contact with thebottom of the tapered hole part, or if it is set, as claimed in claim17, such that, during a period from when the unexpanded expansion partsequentially expands and contacts the bottom of the tapered hole part tocompletion of the construction, the distal end surface of the expansionpart makes always press contact with the bottom of the tapered holepart.

Thus, according to the invention as claimed in claims 16 and 17, theexpanded expansion part making press contact with the tapered surfacecan be more surely prevented from returning to the diameter decreasingdirection, providing a further advantage in terms of enhancement inpulling resistance.

Here, the undercut-type prepared hole required for constructing thepost-construction anchor as claimed in any one of claims 1 to 17 can bedrilled easily by using a drill bit as claimed in claim 18 or 19.

More specifically, according to the invention as claimed in claims 18and 19, in the process of drilling the prepared hole, the straight holepart having smaller diameter is first drilled, and then the preparedhole general part is drilled in such a way as to expand the diameter ofthe straight hole part. And when the depth of the prepared hole reachesa predetermined depth, a part of the prepared hole general part isexpanded in diameter in a taper way to achieve the undercut shape,thereby forming the tapered hole part. Thus, the tapered hole part,which is most important in view of the function, can be worked preciselyand accurately. More specifically, as for the cutter body of the drillbit, with parts other than the undercutting cutter blade orlarge-diameter blade part guided by the prepared hole general part andthe straight hole part, the undercutting cutter blade is graduallyexpanded in diameter to thereby work the tapered hole part. Thus, thetapered hole part can be accurately worked to be concentric with theprepared hole general part and the straight hole part without anyoccurrence of shake and the like of the undercutting cutter blade.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a first embodiment of thepost-construction anchor according to the invention, wherein (A) is afront view depicting an anchor alone, and (B) is a bottom view of FIG.1(A);

FIG. 2 is an exploded diagram illustrating the anchor shown in FIG. 1;

FIG. 3 is a half section illustrating the anchor shown in FIG. 1(A);

FIG. 4 is a cross-sectional illustration that combines the states of theanchor shown in FIG. 1 before and after its expansion part is expanded;

FIG. 5 is cross-sectional illustrations depicting the constructionprocedures of the anchor shown in FIG. 1 step by step;

FIG. 6 is cross-sectional illustrations depicting the constructionprocedures of the anchor shown in FIG. 1 step by step;

FIG. 7 is cross-sectional illustrations depicting the constructionprocedures of the anchor shown in FIG. 1 step by step;

FIG. 8 is a full cross section illustrating the same state as that inFIG. 7(B);

FIG. 9 is a cross section illustrating a second embodiment of thepost-construction anchor according to the invention;

FIG. 10 is a cross section illustrating the expanded anchor shown inFIG. 9;

FIG. 11 is a front view illustrating a third embodiment of thepost-construction anchor according to the invention;

FIG. 12 is an exploded diagram illustrating the anchor shown in FIG. 11;

FIG. 13 is a cross section illustrating the anchor shown in FIG. 11 inthe state of completion of the construction;

FIG. 14 is an exploded diagram illustrating a fourth embodiment of thepost-construction anchor according to the invention;

FIG. 15 is a cross section illustrating the anchor shown in FIG. 14 inthe state of completion of the construction;

FIG. 16 is a half section illustrating a fifth embodiment of thepost-construction anchor according to the invention;

FIG. 17 is a diagram illustrating a sixth embodiment of thepost-construction anchor according to the invention, wherein (A) is aplan view, and (B) is a half section thereof;

FIG. 18 is a diagram illustrating a seventh embodiment of thepost-construction anchor according to the invention, wherein (A) is afront view, and (B) is a bottom view thereof;

FIG. 19 is a cross-sectional illustration depicting thepost-construction anchor shown in FIG. 18;

FIG. 20 is a cross-sectional illustration that combines the states ofthe anchor shown in FIG. 18 before and after its expansion part isexpanded;

FIG. 21 is an enlarged view illustrating the essential part of FIG. 20;

FIG. 22 is a cross-sectional illustration depicting the essential part,showing the process from the right half to the left half of FIG. 20 stepby step;

FIG. 23 is a front view illustrating an eighth embodiment of thepost-construction anchor according to the invention;

FIG. 24 is an exploded diagram illustrating the anchor shown in FIG. 23;

FIG. 25 is a front view illustrating the essential part of a ninthembodiment of the post-construction anchor according to the invention;

FIG. 26 is a front view illustrating a tenth embodiment of thepost-construction anchor according to the invention;

FIG. 27 is an exploded diagram illustrating the anchor shown in FIG. 26;

FIG. 28 is a diagram illustrating an eleventh embodiment of thepost-construction anchor according to the invention, wherein (A) is afront view illustrating an anchor alone, and (B) is a bottom view ofFIG. 28(A);

FIG. 29 is an exploded diagram illustrating the anchor shown in FIG. 28;

FIG. 30 is a cross section illustrating the anchor shown in FIGS. 28 and29 that has been inserted into a prepared hole and a sleeve isunexpanded;

FIG. 31 is a cross section illustrating the state that the sleeve isexpanded from the state in FIG. 30 and the construction is completed;

FIG. 32 is a cross section illustrating the essential part, showing theprocess from the state in FIG. 30 to the state in FIG. 31 step by step;

FIG. 33 is an enlarged view illustrating the essential part of FIG. 31;

FIG. 34 is a front view illustrating a twelfth embodiment of thepost-construction anchor according to the invention;

FIG. 35 is an exploded diagram illustrating the anchor shown in FIG. 34;

FIG. 36 is a cross section illustrating the anchor shown in FIGS. 34 and35 in the state of completion of the construction;

FIG. 37 is a front view illustrating a thirteenth embodiment of thepost-construction anchor according to the invention;

FIG. 38 is a diagram illustrating a fourteenth embodiment of thepost-construction anchor according to the invention, wherein (A) is aplan view thereof, and (B) is an exploded diagram thereof;

FIG. 39 is a diagram illustrating the details of a drill bit fordrilling an undercut-type prepared hole before constructing the anchorof each of the embodiments, wherein (A) is a cross section illustratingthe essential part, and (B) is a cross section along line a-a in FIG.39(A);

FIG. 40 is a cross section illustrating the state that the prepared holeis drilled by the drill bit shown in FIG. 39; and

FIG. 41 is an illustration that combines the states of an undercuttingcutter blade shown in FIGS. 39 and 40 before and after expanded.

BEST MODE FOR CARRYING OUT THE INVENTION

FIGS. 1 to 4 are diagrams illustrating a first preferred embodiment ofthe post-construction anchor according to the invention (hereinafter, itis simply called an anchor). Particularly, FIGS. 1(A) and (B) depict afront view and a bottom view of the anchor, and FIG. 2 depicts anexploded cross section. FIG. 3 depicts a half section of FIG. 1(A), andFIG. 4 depicts a cross section that combines the states of a sleevebefore and after expanded. In addition, the first embodiment correspondsto the invention as claimed in claims 1 to 7.

As shown in FIGS. 1 and 2, an anchor 1 is formed of a hollow cylindricalsleeve 2 and a plug 3 in a roughly stepped shaft form that is press-fitas an expanding member into the sleeve 2.

A plurality of annular grooves 4 is formed on the outer surface of thesleeve 2. In addition to this, the lower half of the sleeve 2 is slit incollets by four radial slit grooves 5, and thus an expansion part 6expandable in diameter are formed. Then, on the inner surface of theexpansion part 6, a engagement groove 7 in an arc shape in cross sectionis formed annularly as the inner diameter thereof is gradually narroweddownward, and a hole part 8 having an ultrasmall diameter is opened inthe lower part from the engagement groove 7.

On the other hand, the plug 3 is designed to have the total length thatis a few times the length of the sleeve 2 including a large-diametershaft part 9 and a small-diameter shaft part 10 downward, in which afemale thread part 11 is formed in the upper end part. In the lower halfof the small-diameter shaft part 10, an annular projecting part 13 in arough sphere that continues to a general part of the small-diametershaft part 10 through a neck part 12 locally constricted, and a taperedsurface 14 smoothly continuing thereto are formed. Thus, it is designedthat the diameter thereof is gradually reduced downward. Morespecifically, the curvature of the annular projecting part 13 isdesigned to the size matching with the engagement groove 7 of the sleeve2, and the maximum diameter of the annular projecting part 13 is formedto have the same dimensions as those of the general part of thesmall-diameter shaft part 10. The diameter is gradually reduced from theannular projecting part 13 toward a distal end shaft part 15 having theultrasmall diameter, and finally it is converged in the diameter of thedistal end shaft part 15. At the most distal end of the distal end shaftpart 15, a flange part 16 having a larger diameter than this is formed.

Then, when the plug 3 is press-fit into the sleeve 2 for combining thesleeve 2 with the plug 3, as shown in FIG. 3, the inner surface of thegeneral part of the sleeve 2 is simply pressed against the top part ofthe annular projecting part 13 of the plug 3. In addition to this, theflange part 16 at the most distal end of the plug 3 passes over the holepart 8 of the sleeve 2, and is locked at the opening edge of the holepart 8. Consequently, the distal end shaft part 15 of the plug 3 and thehole part 8 of the sleeve 2 are engaged with each other in aconcavo-convex way, and the effect of preventing the disengagement isexerted by relative positioning. Therefore, as shown in the samedrawing, the sleeve 2 and the plug 3 are not separated from each otherin the anchor 1 alone before construction. At the same time, the outerdiameter of the large-diameter shaft part 9 of the plug 3 and the outerdiameter of the unexpanded sleeve 2 are designed to have the samedimensions beforehand. Moreover, a plurality of ultrasmall diagonal ribs17 is formed on the outer surface of the large-diameter shaft part 9 ofthe plug 3.

Next, the construction procedures of the anchor 1 will be described withreference to FIGS. 5 to 8 in addition to FIG. 4; an example is giventhat an undercut-type prepared hole 19 is combined.

First, as shown in FIG. 5(A), the undercut-type prepared hole 19 isdrilled in a concrete structure 18 to be the construction object with adrill and the like. This prepared hole 19 is formed in a taper shape inwhich it is expanded in a skirt shape toward the deep side near the holebottom of the prepared hole general part 20 to form a tapered hole part21, and a straight hole part 22 is continuously formed from the holebottom of the tapered hole part 21. The diameter of the straight holepart 22 is formed smaller than that of the prepared hole general part20. In addition, the prepared hole 19 in a special form is drilled by adrill bit for exclusive use, which will be described later.

Subsequently, as shown in FIG. 5(B), the anchor 1 is inserted into theprepared hole 19, the distal end surface of the sleeve 2, that is, thedistal end surface of the expansion part 6 is allowed to reach the holebottom of the tapered hole part 21. Then, with the use of a given jig orwith no jig, the head of the plug 3 is directly hit with a hammer, andis hammered until the upper end surface of the large-diameter shaft part9 is flush with the concrete structure 18 (refer to FIGS. 6 and 7).

In the process of hammering the plug 3, as shown in FIGS. 5(B) and (C),the concavo-convex engagement of the distal end shaft part 15 of theplug 3 described before to the hole part 8 of the sleeve 3 is graduallyreleased as well as the tapered surface 14 of the plug 3 is relativelydisplaced with respect to the expansion part 6 of the sleeve 2.Accordingly, the expansion part 6 is expanded in diameter toward theoutside in a skirt shape so as to follow a tapered surface 21 a of thetapered hole part 21. Then, the annular projecting part 13 of the plug 3is soon engaged into the engagement groove 7 of the sleeve 2 in aconcavo-convex way, and the sleeve 2 is relatively positioned withrespect to the plug 3. Therefore, the hammering of the plug 3 and theexpansion of the expansion part 6 are finally completed in a state thatthe expansion part 6 is pressed against the tapered surface 21 a of thetapered hole part 21.

More specifically, as shown in FIG. 7(B), the total length of the plug 3and the depth of the prepared hole 19 are designed beforehand so thatthe flange part 16 at the distal end of the plug 3 just reaches the holebottom of the straight hole part 22 of the prepared hole 19 when theupper end surface of the plug 3 is flush with the counterpart concretestructure 18. Thus, builders can visually confirm the state that theupper end surface of the plug 3 is flush with the concrete structure 18,and recognize the time to finish hammering by a change in impact soundaccompanied by the plug reaching the bottom. In addition to this, theycan momentarily really know the event that the annular projecting part13 of the plug 3 is engaged into the engagement groove 7 of the sleeve 2in a concavo-convex way as a tactile feel, they consider that thegeneration of this tactile feel tells the expansion part 6 having beenexpanded by a predetermined amount, and then they finish hammering theplug 3.

As shown in FIG. 8, in the state that the expansion part 6 is routinelyexpanded from the root part thereof, they themselves try to return inthe closing direction due to springback. However, in addition to theannular projecting part 13 of the plug 3 being engaged into theengagement groove 7 of the sleeve 2 in a concavo-convex way, thereaction force from the tapered surface 21 a of the tapered hole part 21works on the expansion part 6 as well as the reaction force that isgenerated in association with the plug 3 reaching the hole bottom of thestraight hole part 22 works so as to push back the entire plug 3 upwardat the same time. Consequently, as shown in FIGS. 7(B) and 8, theexpansion part 6 is pressed against the tapered surface 21 a, andself-maintain this state.

More specifically, in the state of completion of the construction, thereaction force of the hole bottom that is generated in association withthe plug 3 reaching the hole bottom of the prepared hole 19 pushes backthe plug 3 itself in the direction opposed to the hammering direction.Consequently, the reaction force of the hole bottom works as a force inthe direction of further expanding the expansion part 6 in the part ofthe concavo-convex engagement. This is nothing more or less than theexpansion part being pressed against the tapered surface 21 a of theprepared hole 19 all the time, and thus the state of completion of theconstruction is self-maintained. These events are not generated that thepressed state becomes insufficient or a clearance is produced.Therefore, the anchor 1 alone can obtain the pulling resistance equal tothe tensile strength of the steel product and the like at the same timeas the construction is completed without relying on the pulling forceand the like.

As described above, according to the embodiment, the plug 3 is simplypress-fit into the sleeve 2 and both are also engaged with each other ina concavo-convex way for relative positioning in the anchor 1 alonebefore construction. Therefore, the sleeve 2 is not separated from theplug 3 with significantly excellent handling-ability, a tactile feel canbe obtained because of the concavo-convex engagement when the plug 3 ishammered to the defined position to expand the expansion part 6. Inaddition to this, it can be visually confirmed that the upper endsurface of the plug 3 is flush with the concrete structure 18, and thestate can be confirmed by a change in impact sound. Thus, variationscaused by differences in individual builders are hard to be generated inthe constructed state, and the stable anchor effect can be obtained allthe time. Furthermore, with the combination of the undercut-typeprepared hole 19, the anchor 1 alone can obtain the pulling resistanceequal to the tensile strength of the steel product and the like at thesame time as the construction is completed without relying on thepulling force and the like, and the pulling resistance thereof isfurther enhanced.

FIGS. 9 and 10 depict a second embodiment of the anchor according to theinvention; the parts common to those in the first embodiment areassigned the same reference numerals and signs. In addition, the secondembodiment corresponds to the invention as claimed in claims 1 to 3 and5 to 7.

An anchor 31 of the second embodiment is different from that of thefirst embodiment in that the shapes of an engagement groove 27 of asleeve 2 and an annular projecting part 23 of a plug 3 are reduced,which are to be engaged with each other in a concavo-convex way byexpanded expansion part 6, and a tapered surface 24 is formed at thedistal end further from the plug 3. Furthermore, since the structureother than the description above is basically the same as that of thefirst embodiment, completely the same advantages as those of the firstembodiment can be obtained in the second embodiment.

FIGS. 11 to 13, 14 and 15 depict third and fourth embodiments of theanchor according to the invention. FIG. 11 depicts a front view, FIGS.12 and 14 depict exploded diagrams, and FIGS. 13 and 15 depict crosssections after a sleeve 2 is expanded. The parts common to those in thefirst and second embodiments are assigned the same reference numeralsand signs. In addition, the third embodiment corresponds to theinvention as claimed in claims 1 to 6 and 8, and the fourth embodimentcorresponds to the invention as claimed in claims 1 to 3, 5, 6 and 8.

In the third embodiment shown in FIGS. 11 to 13, it is different fromthe first embodiment in that a large-diameter shaft part of a plug 33 inan anchor 41 is formed of a long deformed bar for reinforced concrete(deformed steel bar with threads) 29. The deformed bar 29 for reinforcedconcrete also serves as a male thread on which a nut 26 is screwedtogether through a washer 25.

Similarly, in the fourth embodiment shown in FIGS. 14 and 15, it isdifferent from the second embodiment shown in FIGS. 9 and 10 in that alarge-diameter shaft part of a plug 33 in an anchor 51 is formed of along deformed bar for reinforced concrete (deformed steel bar withthreads) 29. The deformed bar 29 for reinforced concrete also serves asa male thread on which a nut 26 is screwed together through a washer 25.

In the construction of the anchors 41 and 51 of the third and fourthembodiments, the expansion part 6 is expanded by completely the sameprocedures as those in the first embodiment, and then the nut 26 istightened with a torque wrench to a defined torque. When this is done,there is an advantage that more accurately controls or ensures thepulling resistance (strength) for the anchors 41 and 51 by the tightenedtorque value. In this case, an adhesive can be combined as well. Any ofthe anchors can be used as a joint bar for earthquake-resistantreinforcement of concrete structures, for example.

FIG. 16 depicts a fifth embodiment of the anchor according to theinvention; the parts common to those in the first embodiment areassigned the same reference numerals and signs. In addition, the fifthembodiment corresponds to the invention as claimed in claims 1 to 7.

As shown in FIG. 16, in an anchor 61 of the fifth embodiment, anextension rod 30 is extended and formed integrally on the upper side ofa large-diameter shaft part 39 in a plug 43. As similar to FIG. 2, afemale thread part for joining a given counterpart structure is formedin a head 30a of the extension rod 30, and a marking 34 for an indicatorin hammering is formed on the border between the large-diameter shaftpart 39 and the extension rod 30. Therefore, it is fine to hammer untilthe marking 34 is flush with a concrete structure 18. Also in the fifthembodiment, completely the same advantages as those of the firstembodiment can be obtained.

FIG. 17 depicts a sixth embodiment of the anchor according to theinvention; the parts common to those in the first embodiment areassigned the same reference numerals and signs. In addition, the sixthembodiment corresponds to the invention as claimed in claims 1 to 7 and9.

An anchor 71 is configured to intend to positively combine an adhesivein its construction. As shown in FIG. 17, helical grooves 35 in a threadgroove form are formed on the outer surface of a large-diameter shaftpart 49 in a plug 53, and notch grooves 36 are formed on a head 49 a soas to communicate with the space between the helical grooves 35.

Thus, when construction is conducted as an adhesive is combined, theholding property of the adhesive is excellent because of the helicalgrooves 35, and air in an adhesive layer can be removed easily from thenotch grooves 36 in construction. Therefore, the anchor effect due tothe adhesive is also exerted surely.

FIGS. 18 and 19 depict a seventh embodiment of the anchor according tothe invention; the parts common to those in the first embodiment shownin FIGS. 1 to 4 are designated the same reference numerals and signs. Inaddition, the seventh embodiment corresponds to the invention as claimedin claims 1 to 3, 5, 7, and 10 to 12.

As shown in FIGS. 18 and 19, an anchor 81 of this embodiment isdifferent from that of the first embodiment in that it has a restraintring 46 having the same outer diameter as that of a large-diameter shaftpart 9 in addition to a sleeve 44 and a plug 45. In plug 45, a middlestep part 47 is formed between the large-diameter shaft part 9 and asmall-diameter shaft part 10, and the restraint ring 46 in a simplehollow cylindrical shape is press-fit and fixed to the middle step part47. It is of course acceptable that the restraint ring 46 is insertedinto the middle step part 47 and then fixed and welded at a few dots.Then, the provision of the restraint ring 46 ensures a given clearance48 between the restraint ring 46 and the small-diameter shaft part 10,and a beveled part 50 is formed on the inner surface at the distal endof the restraint ring 46 as shown in FIG. 21 of an enlarged diagram.

In the sleeve 44, the lower half thereof is slit into collets by sixradial slit grooves 52 to form an expansion part 56 expandable indiameter, and a thin general part 57 is formed, which has a thicknessinsertable into the clearance 48 between the restraint ring 46 and thesmall-diameter shaft part 10 in the upper half other than the expansionpart 56. Then, an annular groove 4 is formed on the general part 57, agroove part 54 (refer to FIG. 21) in an annular groove form similarthereto is formed on the expansion part 56 at the position facing thebeveled part 50 of the restraint ring 46. The sleeve 44 is press-fit toan annular projecting part 13 of the plug 45 so as to slightly enter theinside of the restraint ring 46, and is engaged with a flange part 16 atthe distal end of the plug 45 for preventing disengagement. Furthermore,as apparent from FIG. 18(B), a knurled rough surface is formed on thedistal end surface of the expansion part 56 beforehand.

Therefore, according to the anchor 81 of the seventh embodiment, asshown in FIGS. 20 and 21, the behavior of hammering work in the preparedhole 19 is basically the same as that of the first embodiment. Morespecifically, as shown in FIG. 22(A) in addition to FIGS. 20 and 21,when the plug 45 is hammered in a state that the expansion part 56 ofthe sleeve 44 reaches the bottom of a tapered hole part 21, theexpansion part 56 is gradually expanded outside and closely contactedwith a tapered surface 21a of the tapered hole part 21 (refer to FIGS.21(B) and (C)). Finally, as shown FIG. 21(D), the expansion part 56 isclosely contacted with the tapered surface 21 a of the tapered hole 21,and then the construction is completed in a state that the distal end ofthe plug 45 reaches the hole bottom of a straight hole part 22.

In the expansion process, since the restraint ring 46 is fixed to theplug 45 beforehand, it is relatively displaced with respect to thesleeve 44 along with the plug 45, and the general part 57 of the sleeve44 gradually enters the clearance 48 between the restraint ring 46 andthe small-diameter shaft part 10 of the plug 45. Then, near the end ofin the expansion process of the expansion part 56 and right before thedistal end of the plug 45 reach the hole bottom of the straight holepart 22, the beveled part 50 at the distal end of the restraint ring 46is engaged with and pressed against the groove part 54 on the outersurface of the expansion part 56 as shown in the left half of FIG. 21.Accordingly, the groove part 54, which is an expanded bend part of theexpansion part 56, is strongly restrained by the restraint ring 46 fromoutside so as to stand up to the annular projecting part 13 of the plug45 pressing and spreading the expansion part 56 from the inside of theexpansion part 56. The expanded bend part is pressed and restrained bythe annular projecting part 13 and the restraint ring 46 outside andinside, and then the expansion of the expansion part 56, that is, theconstruction as the anchor 81 is completed.

This is nothing more or less than the expanded state of the expansionpart 56 being in a self-locked state that the expansion part 56 isautonomously locked by the anchor 81 itself, not by the prepared hole 19even though the expansion part 56 is pressed against the tapered surface21 a of the prepared hole 19. The expanding operation of the expansionpart 56 is stably conducted, and springback of the expansion part 56 isnot allowed. Therefore, the embodiment is significantly excellent in theaspect of the working stability.

FIGS. 23 and 24 depict an eighth embodiment of the anchor according tothe invention; the parts common to those in the third embodiment shownin FIGS. 11 to 13 and the seventh embodiment shown in FIGS. 18 and 19are assigned the same reference numerals and signs. In addition, theeighth embodiment corresponds to the invention as claimed in claims 1 to3, 5, 7, 8 and 10 to 12.

More specifically, in the eighth embodiment shown in FIGS. 23 and 24, asleeve 44 and a restraint ring 46 the same as those shown in FIGS. 18and 19 are adapted to an anchor 91 having a large-diameter shaft part ofa plug 33 formed of a deformed bar 29 for reinforced concrete.

Furthermore, FIG. 25 depicts a ninth embodiment of the anchor accordingto the invention; the parts common to those in the fifth embodimentshown in FIG. 16 and the seventh embodiment shown in FIGS. 18 and 19 areassigned the same reference numerals and signs. In addition, the ninthembodiment corresponds to the invention as claimed in claims 1 to 3, 5,8 and 10 to 12.

More specifically, in the ninth embodiment shown in FIG. 25, a sleeve 44and a restraint ring 46 the same as those shown in FIGS. 18 and 19 areadapted to an anchor 101 in which an extension rod 30 is extended andformed from a large-diameter shaft part of a plug 43.

Moreover, FIGS. 26 and 27 depict a tenth embodiment of the anchoraccording to the invention; the parts common to those in the sixthembodiment shown in FIG. 17 and the seventh embodiment shown in FIGS. 18and 19 are assigned the same reference numerals and signs. In addition,the tenth embodiment corresponds to the invention as claimed in claims 1to 3, 5, 7, 9 and 10 to 12.

More specifically, in the tenth embodiment shown in FIGS. 26 and 27, asleeve-44 and a restraint ring 46 the same as those shown in FIGS. 18and 19 are adapted to an anchor 111 in which helical grooves 35 forholding an adhesive are formed on the outer surface of a large-diametershaft part 49 in a plug 53.

Also in each of the eighth, ninth and tenth embodiments, the sameadvantages as those of the seventh embodiment can be obtained.

FIGS. 28 and 29 depict an eleventh embodiment of the anchor according tothe invention; the parts common to those in the first embodiment shownin FIGS. 1 to 4 are assigned the same reference numerals and signs. Inaddition, the eleventh embodiment corresponds to the invention asclaimed in claims 1 to 3, 5 to 7, and 13 to 17. As shown in FIGS. 28 and29, the lower half of a sleeve 102 forming an anchor 121 with a plug 3is slit into collets by six radial slit grooves 103 to form an expansionpart 106 expandable in diameter. The expansion part 106 has an expandingclaw part 106a at the distal end thereof and an auxiliary expanding clawpart 106b integrally formed at the root part of the expanding claw part106a. As shown in FIG. 31, when the construction is completed as theexpansion part 106 is expanded, the expanding claw parts 106 a arepressed against a tapered surface 21 a of a tapered hole part 21 of aprepared hole 19 as well as the auxiliary expansion part 106 b isplastically deformed outside and engaged in the inner surface of aprepared hole general part 20 at the same time.

Moreover, an annular projecting part 104 and a tapered surface 105 areformed at the distal end part of a small-diameter shaft part 10 in theplug 3, and a taper-shaped engagement groove 107 is formed in the innersurface of the expansion part 106 in the sleeve 102, the engagementgroove is to be engaged with the annular projecting part 104 in aconcavo-convex way as the expansion part 106 is expanded. Furthermore,as shown in FIG. 33, two narrow straight parts 108 and 109 in acylindrical shape are formed near the top part of the annular projectingpart 104 so as to adjoin to the annular projecting part 104, and a ridgepart 110 relatively sharp is formed on the distal end part further fromthe straight parts 108 and 109.

Therefore, according to the anchor 121 of the eleventh embodiment, asshown in FIG. 30, the sleeve 102 is inserted into the prepared holegeneral part 20 of the prepared hole 19 along with the plug 3, and theplug 3 is hammered as the distal end surface of the sleeve 102 reachesthe hole bottom of the tapered hole part 21. Then, as shown in FIG. 31,the annular projecting part 104 of the plug 3 and the engagement groove107 of the sleeve 102 are engaged with each other in a concavo-convexway, the expansion part 106 is expanded, the expanding claw parts 106 aare pressed against the tapered surface 21 a of the tapered hole part21, the auxiliary expanding claw parts 106 b plastically deformed areengaged in the inner surface of the prepared hole general part 20, andthen the construction is completed. In addition, FIGS. 32(A) to (D)depict the process from the state in FIG. 30 to the state in FIG. 31step by step more in detail. More specifically, in addition to theanchor effect due to the expansion of each of the expanding claw parts106 a, the anchor effect due to the auxiliary expanding claw parts 106 bbeing engaged in the prepared hole general part 20 is obtained, and thusthe pulling resistance after the construction is completed is furtherenhanced.

In the process of expanding the expansion part 106, as shown in FIG. 32,the expansion proceeds as the distal end surfaces of the expanding clawparts 106 a are always pressed against the hole bottom of the taperedhole part 21. As shown in FIGS. 31 and 33, the construction is completedin the state that the distal end surfaces of the expanding claw parts106 a are pressed against the hole bottom of the tapered hole part 21 ofthe prepared hole 19. At the same time, as shown in FIG. 33, the ridgepart 110 of the plug 3 is pressed against the inner surfaces of theexpanding claw parts 106 a. Therefore, because of the frictional forcebetween the distal end surfaces of the expanding claw parts 106 a andthe hole bottom of the tapered hole part 21 and the frictional forcebetween the ridge part 110 and the inner surfaces of the expanding clawparts 106 a, a returning phenomenon, which is so-called springback ofthe expanding claw parts 106 a, is suppressed in the middle of expansionor in the state of completion of the construction.

Furthermore, as apparent from FIG. 28(B), the distal end surfaces of theexpanding claw parts 106 a are formed with a knurled rough surfacebeforehand.

Moreover, as shown in FIG. 33, in the state of completion of theconstruction, a part of the engagement groove 107 of the expanding clawparts 106 a and a projecting part 111 at the end part of the engagementgroove 107 are pressed against the two straight parts 108 and 109adjoining to the annular projecting part 104. Thus, for example, eventhough the pulling force works on the plug 3 after the construction iscompleted and the plug 3 and the expansion part 106 is relativelydisplaced slightly in the axial direction, the relative displacementdoes not immediately produce the force of reducing the expanding clawparts 106 a in diameter as long as they are relatively displaced overthe width of the straight parts 108 and 109, not producing a clearancebetween the expanding claw parts 106 a and the tapered surface 21 a ofthe tapered hole part 21. Accordingly, this also suppresses thephenomenon of each of the expanding claw parts 106 a returning in thedirection of reducing the diameter, and the pulling resistance isfurther enhanced.

FIGS. 34 to 36 depict a twelfth embodiment of the anchor according tothe invention. FIG. 34 depicts a front view, FIG. 35 depicts an explodeddiagram, and FIG. 36 depicts a cross section after a sleeve 102 isexpanded. The parts common to those in the eleventh embodiment areassigned the same reference numerals and signs. In addition, the twelfthembodiment corresponds to the invention as claimed in claims 1 to 3, 5,6, 8 and 13 to 17.

In the twelfth embodiment shown in FIGS. 34 to 36, it is different fromthe eleventh embodiment in that a large-diameter shaft part of a plug 33in an anchor 131 is formed of a long deformed bar for reinforcedconcrete (deformed steel bar with threads) 29 the same as that in thethird and fourth embodiments (refer to FIGS. 11 to 15). The deformed bar29 for reinforced concrete also serves as a male thread on which a nut26 is screwed together through a washer 25.

The construction procedures of the anchor 131 of the twelfth embodimentare completely the same as those in the third and fourth embodimentsshown in FIGS. 11 to 15, and completely the same effects and advantagesas those of the eleventh embodiment can be obtained.

FIG. 37 depicts a thirteenth embodiment of the anchor according to theinvention; the parts common to those in the eleventh embodiment areassigned the same reference numerals and signs. In addition, thethirteenth embodiment corresponds to the invention as claimed in claims1 to 3, 5 to 7 and 13 to 17.

As shown in FIG. 37, an anchor 141 of the thirteenth embodiment isdifferent from that of the eleventh embodiment in that an extension rod30 similar to that in the fifth embodiment (refer to FIG. 16) isextended and formed integrally on the upper side of a large-diametershaft part 39 in a plug 43. A female thread part for joining a givencounterpart structure is formed at a head 30a of the extension rod 30 assimilar to FIG. 29, and a marking 34 for an indicator in hammering isformed on the border between the large-diameter shaft part 39 and theextension rod 30. Also in the thirteenth embodiment, completely the sameadvantages as those of the eleventh embodiment can be obtained.

Furthermore, FIG. 38 depicts a fourteenth embodiment of the anchoraccording to the invention; the parts common to those in the eleventhembodiment are assigned the same reference numerals and signs. Inaddition, the fourteenth embodiment corresponds to the invention asclaimed in claims 1 to 3, 5 to 7, 9 and 13 to 17.

In an anchor 151 of the fourteenth embodiment, helical grooves 35 in athread groove form similar to those in the sixth embodiment (refer toFIG. 17) are formed on the outer surface of a large-diameter shaft part49 in a plug 53, and notch grooves 36 are formed on a head 49 a so as tocommunicate with the space between the helical grooves 35.

Therefore, the construction procedures of the anchor 151 of thefourteenth embodiment are completely the same as those of the sixthembodiment shown in FIG. 17, and completely the same effects andadvantages as those of the eleventh embodiment can be obtained.

Here, as for a drill bit for drilling the prepared hole 19 in a specialform that is needed in the construction of the anchor of each of theembodiments, for example, the prepared hole can be worked easily withthe use of the drill bit that is improved based on the drill describedin a brochure of WO 01/06070.

More specifically, FIGS. 39 to 41 depict the general configuration ofthe drill bit improved for constructing the anchor of each of theembodiments. A cutter body 182 in a hollow cylindrical shape at thedistal end of a drill bit 181 is mounted with a straight hole cutterblade 183 to be a small-diameter blade part by brazing and the like soas to cross in the diameter direction. At the positions upward near thestraight hole cutter blade 183 and facing to each other as the straighthole cutter blade 183 is sandwiched, that is, at the positions shiftedin the phase at 90 degrees with respect to the straight hole cutterblade 183, undercutting cutter blades 184 are mounted, which are alarge-diameter blade part movable or rocking opening and closing.Furthermore, a slidable operating rod 185 is inserted into the cutterbody 182 beforehand.

Moreover, in the undercutting cutter blades 184, a hook part 186 thereofis engaged with a holding lock part 187 at the lower end of theoperating rod 185. The force of lifting the operating rod 185 generallyworks, and thus the undercutting cutter blades 184 are unexpanded asshown in FIG. 39(A). However, the operating rod 185 is pressed downwardto expand each of the undercutting cutter blades 184 as they are rocked,as shown in FIGS. 40 and 41.

Therefore, when the distal end of the cutter body 182 is pressed againsta concrete structure 18 to start drilling work as the drill bit 181 isrotated and driven, the straight hole cutter blade 183 at the distal endof the cutter body 182 and the undercutting cutter blades 184 graduallyproceed to drill the prepared hole 19. At this time, the straight holecutter blade 183 first works the straight hole part 22 at the farthestend. Subsequently, the undercutting cutter blades 184 drill the preparedhole general part 20 having a larger diameter than that of the straighthole part 22 so as to expand the straight hole part 22 in diameter. Morespecifically, in the middle of drilling the prepared hole, it is alwaysin a so-called stepped prepared hole shape formed of the straight holepart 22 and the prepared hole general part 20 having a larger diameterthan that of the straight hole part 22.

In the meantime, the operating rod 185 is pressed downward at the timewhen the depth of the prepared hole 19 in the middle of drilling becomesa predetermined depth, and then the undercutting cutter blades 184 arerocked and gradually expanded outside. Accordingly, the straight holecutter blade 183 drills the straight hole part 22 so as to furtherincrease the depth of the prepared hole 19 having been in the givendepth before, and the undercutting cutter blades 184 expand the upperstep part of the straight hole part 22 in diameter to be the taperedhole part 21 having the tapered surface 21 a (refer to FIG. 5(A)).

As described above, according to the drill bit 181, the straight hole isfirst worked, the operating rod 185 is pressed in at the time when thestraight hole reaches the predetermined depth as similar to the generaldrilling work, and then the tapered hole part 21 to be the undercut partis autonomously worked. Therefore, the prepared hole 19 having thetapered hole part 21 in the undercut shape can be worked with completelythe same perception as that of the general drilling work and with nocomplicated operations for the drill bit 181.

More specifically, in working the tapered hole part 21, which isfunctionally most important, the cutter body 182 of the drill bit 181 isoperated in which the undercutting cutter blades 184 are graduallyexpanded in diameter to work the tapered hole part 21 in the state thatthe parts other than the undercutting cutter blades 184 to be thelarge-diameter blade part are guided by the prepared hole general part20 and the straight hole part 22. Thus, a shake and the like are notgenerated in the undercutting cutter blades 184, and the tapered holepart 21 can be worked accurately, concentrically with the prepared holegeneral part 20 and the straight hole part 22.

1. A post-construction anchor comprising a sleeve having an expansionpart and a plug formed with a tapered part inserted into the sleeve forexpanding the expansion part, the anchor being adapted to anundercut-type prepared hole having near a bottom thereof a diameterexpanded in a taper way, characterized in that when the plug is hammeredwith the sleeve contacting the bottom of the prepared hole, an innerperipheral surface of the expansion part is engaged with an outerperipheral surface of the plug in a concavo-convex way as the expansionpart expands until the expansion part makes close contact with thetapered surface of the prepared hole in accordance with relativedisplacement between the expansion part and the plug, and that, at thesame time, by a hole-bottom reaction force generated by the plugcontacting the bottom of the prepared hole, a construction is completedwith the expansion part making press contact with the tapered surface ofthe prepared hole.
 2. The post-construction anchor as claimed in claim1, characterized in that an annular engagement groove is formed in theinner peripheral surface of the expansion part, and an annularprojecting part is formed on the outer peripheral surface of the plug,and that the engagement groove is engaged with the annular projectingpart in a concavo-convex way when the expansion part expands to contactthe tapered surface of the prepared hole in accordance with the relativedisplacement between the expansion part and the plug.
 3. Thepost-construction anchor as claimed in claim 1 or 2, characterized inthat, with the expansion part being unexpanded, a flange part at adistal end of the plug is locked at an inner periphery opening edge at adistal end of the sleeve for preventing disengagement of the sleeve fromthe plug.
 4. The post-construction anchor as claimed in claim 3,characterized in that, with the expansion part being unexpanded, theouter peripheral surface of the plug is engaged with the innerperipheral surface of the sleeve in a concavo-convex way for preventingdisengagement of the plug from the sleeve, and as a consequence, theflange part at the distal end of the plug is locked at an innerperiphery opening edge at the distal end of the sleeve for preventingdisengagement of the sleeve from the plug.
 5. The post-constructionanchor as claimed in claim 4, characterized in that the prepared hole isformed with a straight hole part having a diameter smaller than that ofa prepared hole general part, the straight hole part being continuouslyformed with a bottom of a tapered hole part having a diameter expandedin a taper way, and that the unexpanded expansion part contacts thebottom of the tapered hole part prior to expansion of the expansionpart, whereas the distal end of the plug contacts a bottom of thestraight hole part upon completion of the construction.
 6. Thepost-construction anchor as claimed in claim 5, characterized in thatthe plug is formed in a stepped shank, and that the unexpanded sleeve isinserted into and supported in a small-diameter shank part to therebyset an outer diameter of a general part of the plug and that of ageneral part of the unexpanded sleeve at roughly the same dimension. 7.The post-construction anchor as claimed in claim 6, characterized inthat the plug is formed with a female thread part.
 8. Thepost-construction anchor as claimed in claim 6, characterized in thatthe plug includes a deformed bar for reinforced concrete.
 9. Thepost-construction anchor as claimed in claim 7, characterized in thathelical grooves of thread groove shape are formed in the outerperipheral surface of the plug.
 10. The post-construction anchor asclaimed in claim 9, characterized in that the plug is formed with arestraint ring which can receive a part of the sleeve, and that, at thefinal stage of expanding the expansion part, an end of the restraintring abuts on the outer peripheral surface of the expansion part torestrain an expanded bend part.
 11. The post-construction anchor asclaimed in claim 10, characterized in that a groove engaged with the endof the restraint ring is formed in the outer peripheral surface of theexpansion part.
 12. The post-construction anchor as claimed in claim 11,characterized in that the restraint ring is fixed to the plug beforehandby press-fit or welding.
 13. The post-construction anchor as claimed inclaim 2, characterized in that the annular projecting part of the outerperipheral surface of the plug at a part near the top includes acylindrical straight part, and that when the expansion part expands tocontact the tapered surface of the prepared hole, a part of theengagement groove makes close contact with a part of the straight part.14. The post-construction anchor as claimed in claim 13, characterizedin that the prepared hole is formed with a straight hole part having adiameter smaller than that of a prepared hole general part, the straighthole part being continuously formed with a bottom of the tapered holepart having a diameter expanded in a taper way, and that the unexpandedexpansion part contacts the bottom of the tapered hole part prior toexpansion of the expansion part, whereas the distal end of the plugcontacts a bottom of the straight hole part upon completion of theconstruction.
 15. The post-construction anchor as claimed in claim 14,characterized in that the expansion part has an expanding claw and anauxiliary expanding claw on the root side of the expanding claw, andthat, in parallel with the expanding claw part making press contact withthe tapered surface of the tapered hole part, the auxiliary expandingclaw is plastically deformed and engaged in an inner peripheral surfaceof the prepared hole general part upon completion of the construction.16. The post-construction anchor as claimed in claim 15, characterizedin that the construction is completed with a distal end surface of theexpansion part makes press contact with the bottom of the tapered holepart.
 17. The post-construction anchor as claimed in claim 16,characterized in that, during a period from when the unexpandedexpansion part sequentially expands and contacts the bottom of thetapered hole part to completion of the construction, the distal endsurface of the expansion part makes always press contact with the bottomof the tapered hole part.
 18. A drill bit for drilling an undercut-typeprepared hole prior to the construction of a post-construction anchoradapted to the prepared hole, the prepared hole having near a bottomthereof a tapered hole part having a diameter expanded in a taper wayand a straight hole part having a diameter smaller than that of aprepared hole general part, the straight hole part being continuouslyformed with a bottom of the tapered hole part, characterized in that asmall-diameter blade part is provided to a cutter body at a distal endthereof for drilling the straight hole, and a large-diameter blade partis provided to the cutter body on the side opposite to thesmall-diameter blade part for drilling the prepared hole general part,the large-diameter blade part being swingable and retractable radially,that, in a process of drilling the prepared hole, the small-diameterblade part first drills the straight hole part, and then thelarge-diameter blade part in the unexpanded diameter state drills theprepared hole general part in such a way as to expand the diameter ofthe straight hole part, and that, when a depth of the prepared holereaches a predetermined depth, the large-diameter blade part protrudesswingably radially to thereby expand the diameter of the large-diameterblade part, expanding the diameter of a part of the prepared holegeneral part close to the straight hole part in a taper-way, thusworking the tapered hole part.
 19. The drill bit for working theprepared hole as claimed in claim 18, characterized in that thesmall-diameter blade part includes a straight hole cutter blade, and thelarge-diameter blade part includes an undercutting cutter blade, andthat an operating rod inserted into the cutter body concentricallytherewith is engaged with the undercutting cutter blade, and theundercutting cutter blade has a diameter expanded in accordance withslide displacement of the operating rod.